One of our customers pointed to the following section as being problematic:

Section 8.2.4 (6.2.4 in JSR 289)
"When a SipSession terminates, either because the parent application
session timed out or because the SipSession was explicitly invalidated, the
container MUST purge all state of that SipSession from its memory. In such
a case, if a subsequent request or response belonging to the corresponding
dialog is received, the container is free to handle it in either of the
following ways:
1.Reject the request by sending a 481 error response or
2.Route the request or response without application involvement"

To maintain portability, the spec needs to decide on one way or another, or
it should provide a way to an app to select a preferred one (which might be
difficult when there are multiple apps installed).

Choosing one way and making it mandatory is the easier option to resolve
this issue, so we support that at this point. (The way to go #1 or #2 will
need to be voted on by the EG)